Drug solubilization studies with a variety of bile salt solutions, aqueous and nonaqueous, will be followed using 1H and 13C nmr and also by spectrophotometry. These same techniques will be used to study drug interactions and reactivity in aqueous solutions in the presence and absence of bile salts. Spontaneous decarboxylation occurs in metabolic processes. 6-Nitrobenzisozole-3-carboxylate anion and other carboxylate anions will be used to follow this process in the presence and absence of bile salts. These chemicals will serve as models for metabolites. The self-association of the sodium salts of lithocholic acid and taurocholic acid in isotonic saline will be studied by sedimentation equilibrium experiments. Lithocholic acid has been implicated in cancer of the colon. Ancillary experiments on these compounds - determination of the parital specific volumes and refractive index increments - will also be done. Factors influencing the association will be pursued. Studies will also be carried out on anides of some bile acids by vapor pressure osmometry in aqueous solution. Besides studying the self-association of these compounds, we can also study interaction of these compounds with various substrates (drugs, lipids).